1. Field of the Invention
The present invention relates to a backlight module, and more particularly, to a backlight module capable of reducing the warpage of its optical film.
2. Description of the Prior Art
The display panel and the panel display apparatus using the display panel have become the mainstream among all kinds of display apparatuses. For example, a lot of display panels are used in panel display screens, home flat TVs, monitors of the personal computer, notebook, cell phone, and digital camera. Especially, in recent years, the market demand for LCD apparatus has highly increased. In order to meet the function and appearance requirements of the LCD apparatus, the design of the backlight module used in the LCD apparatus also becomes more diversified.
FIG. 1A and FIG. 1B illustrate a schematic diagram of a conventional backlight module. The conventional backlight module includes a frame 10 and a brightness enhancement film 30. The brightness enhancement film 30 is disposed in the frame 10 and used for changing the optical properties of the lights generated by the below light source to generate the backlight to meet the needs of display panel. A plurality of prisms 31 is formed on the brightness enhancement film 30 extending along a prism direction 33. When the backlight module or the display apparatus including the backlight module is heated, for example, the backlight module or the display apparatus is under an environmental test or used in a poor cooling space, the brightness enhancement film 30 will be heated and expanded to increase its area. Since the plurality of prisms 31 are formed on the brightness enhancement film 30, the extending length of the brightness enhancement film 30 along the prism direction 33 is longer than the extending length of the brightness enhancement film 30 vertical to the prism direction 33.
As shown in FIG. 1B, when the brightness enhancement film 30 extends and expands along the prism direction 33, the brightness enhancement film 30 will interfere with or touch against a sidewall 11 of the frame 10. Since the inner space of the frame 10 is limited, when the brightness enhancement film 30 touches against the sidewall 11, the brightness enhancement film 30 will be warped or wavy, so that the light processing of the brightness enhancement film 30 will be affected, and the quality of the output lights will be lowered.